Generally, during fishing, a spinning reel handle is operated to rotate the rotary frame and to wind the line onto the spool to wind in a hooked fish, at which time there is a risk that the line, when subjected to a large load, will be snapped.
Therefore, in an attempt to avoid this problem, a drag mechanism is incorporated in the reel body of the spinning reel. The drag mechanism has dragging members connected to the reel body, dragging members connected to the spool shaft, and a dragging knob for adjusting the drag force applied by both of the dragging members, the drag knob being operated to apply a desired resistance to rotation of the spool corresponding to the durability of the line.
Where the hooked fish abruptly pulls the line by an unexpectedly large force, the drag knob should be adjusted to reduce the rotational resistance applied to the spool, but such adjustment is difficult to carry out quickly, often resulting in snapping of the line, or too great a reduction in the rotational resistance, thus allowing the hooked fish to escape.